1. Technical Field
The present invention relates generally to hatches and similar apparatus for controlling access to installations such as submersible pump stations, pits, sewers, manholes, vaults, cellars, chutes, chambers, large receptacles, confined spaces, and the like. The present invention relates more particularly to a hatch which includes certain safety features to protect against a fall through the hatch and prevent unauthorized entry to a confined space.
2. Background Art
Access hatches and similar devices have been in use, in one form or another, for hundreds of years. A representative sample of such devices are disclosed in the following U.S. Pat. No. 4,266,380 to Samolis (1981) U.S. Pat. No. 3,521,537 to Forni et al. (1970); U.S. Pat. No. 3,198,094 to Dunkerley (1965); U.S. Pat. No. 1,523,191 to Gilfoy (1925); U.S. Pat. No. 1,442,737 to Schacht (1923); U.S. Pat No. 1,244,501 to Jackson (1917); U.S. Pat. No. 1,068,856 to Clay (1913); U.S. Pat. No. 736,714 to Gendron (1903); U.S. Pat. No. 705,679 to Knapp et al. (1902); U.S. Pat. No. 202,373 to Purtell (1878); U.S. Pat. No. 195,965 to Straight (1877); U.S. Pat. No. 14,359 to Jenks (1856); and U.S. Pat. No. 14,107 to Moore (1856).
The hatches disclosed in these patents all present a potential safety hazard, in that the worker is usually exposed to an open hole when he or she is opening or closing the hatch door, cover, grate, etc. For example, to open or close the hinged grates in U.S. Pat. No. 4,266,380 to Samolis, the worker has to grasp the free side (opposite the hinged side) of the grate. This arrangement encourages the worker to stand near the free sides of the grates or to reach over the grates, exposing the worker to the hole as the grates are opened. A similar example is shown in U.S. Pat. No. 736,714 to Gendronxe2x80x94the handle is located at the free side of the door. A different example is shown in U.S. Pat. No. 3,198,094 to Dunkerley, where a handle to a door lever is located at the free side of a hinged door. The position of the handle encourages the worker to stand near or reach over to the free side of the door, thus exposing the worker to the risk of a fall. Thus, a need persists to improve upon the safety of hatches, especially during the process of opening and closing the hatches.
Another safety issue presented by hatches concerns the requirement that an adequate barrier be erected around the hatch opening. A number of attempts have been made to incorporate such a barrier into the hatch design itself, to eliminate the need for a separate barrier. Examples of such attempts are disclosed in the following U.S. Pat. No. 5,241,789 to Vacelet (1993); U.S. Pat No. 4,266,380 to Samolis; U.S. Pat. No. 1,442,737 to Schacht; U.S. Pat. No. 1,244,501 to Jackson; U.S. Pat. No. 705,679 to Knapp et al.; U.S. Pat. No. 195,965 to Straight; U.S. Pat. No. 14,359 to Jenks; and U.S. Pat. No. 14,107 to Moore. Some of these designs have met with some success. However, they suffer from certain drawbacks. Some of these designs require an interconnection, by way of fasteners, clips or chains, between the xe2x80x9cbarrier componentsxe2x80x9d (e.g., plates or grates) and the hatch cover. This arrangement creates the possibility that if such an interconnection fails, the entire barrier may fail. Fasteners, clips and chains are prone to failure over the useful life of the hatch. Another drawback is the complexity of the moving parts associated with the barrier components and the increased complexity of the hatch cover design. Such complexity leads to increased costs, maintenance and repair for the hatch. Thus, there is a need for a simple, reliable, and inexpensive approach to providing a barrier function in a hatch design.
Another safety issue is whether protection is afforded a worker against falling through the hatch opening (i.e., xe2x80x9cfall-through protectionxe2x80x9d). A falling hazard can arise even where the hatch provides some means of fall-through protection. For example, U.S. Pat. No. 5,265,974 (1993) to Dargie describes a xe2x80x9csafety netxe2x80x9d for the hatch opening. Such a device may be adequate to prevent a fall through the hatchway. However, the net is to be pushed aside, like a shower curtain, to gain access through the hatch. The worker could inadvertently leave the net open after work is completed and the hatch is closed, thus creating a hazard to the next worker who opens the hatch. Thus, a need exists for fall-through protection that is less prone to human error.
The hazard of falling through a hatchway can be further reduced if the worker can perform certain work while the existing fall-through protection is in-place. Such an objective can be achieved if the fall-through protection permits limited access through the hatch. Also, in cases where apparatus connected to a utility line (e.g., a cable or hose) is to be brought up through the hatch for maintenance, the above objective can be achieved with fall-through protection that can be put back in-place once the apparatus is brought up for maintenance. The patents cited herein fail to address such additional versatility in fall-through protection for hatches.
There are instances when a worker may only need to look through a hatch and not enter through it. For example, a worker may need only to visually inspect equipment installed in a pit. In such a case, a worker, who is not trained or certified to enter the pit, can be assigned to such duties. However, once the hatch cover is opened, the untrained or uncertified worker may be tempted to enter the pit. It would therefore be advantageous to provide direct means for controlling the removal of the fall-through protection (e.g., the opening of a grate). For example, for a hatch having a cover and grate, a lock can be employed separately for the grate. An untrained or uncertified worker would be denied access to a key for the grate, thus preventing unauthorized entry.
It is therefore an object of the present invention to provide an access hatch that avoids the limits and problems associated with the prior art.
It is another object of the present invention to provide an access hatch that prompts a worker to stand at a safe location when opening and closing the hatch.
It is a further object of the present invention to provide an access hatch with a grate, wherein the grate self-locks in an open position to provide a secure barrier on one side of the hatch.
It is yet another object of the present invention to provide an access hatch with a grate, wherein a simple self-locking hinge is provided to lock the grate in an open position.
It is yet a further object of the present invention to provide an access hatch with fall-through protection that is substantially immune from human error.
It is still another object of the present invention to provide an access hatch with fall-through protection, wherein the fall-through protection must be in-place before the hatch cover can be closed by a worker, thus ensuring that the fall-through protection is in place for the next worker who opens the hatch.
It is still a further object of the present invention to provide limited access through the hatch even though fall-through protection is in place, thus allowing a worker to perform minor maintenance tasks without removing the fall-through protection.
It is yet still another object of the present invention to provide an access hatch with fall-through protection that can be put back in-place once apparatus, connected to a utility line (e.g., a cable or hose), is brought up through the hatch for maintenance.
It is yet still a further object of the present invention to provide an access hatch with fall-through protection, wherein direct means are provided for controlling the removal of the fall-through protection, to prevent unauthorized entry.
These and other objects are attained in accordance with the present invention, wherein there is provided an access hatch having a frame, a grate, and a pull member or arm pivotally coupled to the grate. The frame contains an access opening. The grate has a near side and a far side. The near side is coupled to the frame for pivotal movement of the grate between a closed and an open position. In the closed position, the grate lies substantially in the access opening of the frame and blocks at least a portion of the opening. In the open position, the grate is oriented away from the opening of the frame to allow access through the opening. The pull member has a proximal end and a distal end. The distal end is pivotally coupled to the grate, near the far side of the grate, such that the proximal end is moveable away from the grate from a rest position. The proximal end extends substantially to the near side of the grate when the proximal end is in the rest position. The proximal end is normally in the rest position when the grate is in the closed position. A worker, intending to open the grate, is prompted to stand at the near side of the grate and grasp the proximal end of the pull member, to pull the grate to the open position.
In the preferred embodiment, the access hatch further comprises a cover mounted to the frame for pivotal movement between an open position (away from the frame) and a closed position (over the frame). The grate and cover are disposed on the frame such that movement of the cover, from the open to the closed position, is obstructed by the grate when the grate is in the open position, and is clear of the grate when the grate is in the closed position. Thus, the cover cannot be closed until the grate is closed.
In the preferred embodiment, the pull member includes a catch extending from its distal end. The catch is adapted to engage the frame when the grate is in the closed position and the pull member is in the rest position. This engagement locks the grate in the closed position. The pull member may further include an eyelet at its proximal end, to receive a fastener, such as a padlock. In this case, the grate contains a hole which is aligned with the eyelet when the pull arm is in the rest position. The padlock or other fastener is inserted through the aligned hole and eyelet to lock the pull arm to the grate.
In the preferred embodiment, the grate is coupled to the frame by way of a locking hinge. The hinge includes a male link member coupled to a female link member. One of the link members is rotatable relative to the other of the link members. The male link member lockingly engages the female link member at a locking point of rotation. The link members are oriented relative to the frame and grate such that the locking point of rotation occurs when the grate is in the open position. The grate is locked in the open position upon engagement of the male and female link members.
In the preferred embodiment, the near side of the grate is spaced apart from the frame so as to define a limited access opening between the frame and grate. This allows limited access through the grate when the grate is in the closed position.
In the preferred embodiment, the grate includes a perimeter containing a recessed portion. The recessed portion forms a utility opening with the frame when the grate is in the closed position. An apparatus connected to a utility line can pass through the access opening when the grate is in the open position, and rest on top of the grate when the grate is in the closed position. This is possible because the utility line is able to pass through the utility opening.
The present invention also contemplates a hatch with more than one grate and cover. In a preferred embodiment, a pair of grates and corresponding covers are employed. In such an embodiment, a utility opening may be defined by two complementary recesses, one contained in each grate. Alternatively, the utility opening may be defined by two complementary recesses and the frame.